Efficient address assignment in coded lighting systems

ABSTRACT

Coded light has been proposed to enable advanced control of light sources and transmit information using light sources. It is based on invisibly embedding of data and identifiers in their light output. Methods, devices and systems configured to efficient assignment of addresses in a coded lighting system, still allowing for unique identification, are proposed. More specifically, the assignment of addresses occurs in two phases, where in the initial phase wide area unique addresses are used, while in the second phase only local area unique addresses are used. Also, methods, devices and systems configured to efficiently distribute a set of addresses over a set of light sources in this second phase, to maximize the performance of the illumination contribution estimation, and positioning, are disclosed.

FIELD OF THE INVENTION

The present invention relates to operating a lighting system.Particularly it relates to methods and devices for operating a lightingsystem comprising a plurality of light sources each of which is enabledto emit coded light.

BACKGROUND OF THE INVENTION

Coded light (CL) has been proposed to enable advanced control of lightsources. Coded light is based on embedding of data, inter alia invisibleidentifiers, in the light output of the light sources. Coded light maythus be defined as the embedding of data and identifiers in the lightoutput of a visible light source, wherein the embedded data and/oridentifier preferably do not influence the primary lighting function(i.e. illumination) of the light source. Hence, any modulation of theemitted light pertaining to data and/or identifier should be invisibleto humans. This allows for applications such as interactive scenesetting, commissioning and re-commissioning of networked lightingsystems. Coded light may be used in communications applications whereinone or more light sources in a coded lighting system are configured toemit coded light and thereby communicate information to a receiver. Alsothe light sources of the coded lighting system may be capable ofbidirectional communications utilizing coded light. Thus coded light maybe associated with the term visible light communication.

In a CL system, it may be desirable to identify and control the lightsources in a given environment or in the proximity of a user oroperator. For typical office environments such a coded lighting systemmay include in the order of 5 to 10 light sources. For future ambientcreation systems (inter alia for retail) based on light emitting diodes(LEDs) the number of light sources could be at least one order higher,i.e. 20 to 200 light sources.

For identification and control of each light source, a light sourceshould be distinguishable from all other light sources in the controlnetwork, not only local. In office environments, as an example, thiscontrol network may cover the whole building and might include 1000light sources. The CL address space assigned for this environment shouldthen at least include 1000 addresses, hence corresponding to 10 binarydigits (bits).

In some system architectures, it might moreover be required to transmitcoded light comprising a specific address format which might be evenmuch longer. For example, in a first commissioning phase the lightsources might be required to transmit the Internet protocol (IP) ormedia access control (MAC) addresses of the local lighting controller,inter alia based on the digital addressable light interface (DALI),followed by the assigned control address of the light sources, interalia the DALI address. This might result in addresses of 70 bit length.Alternatively, a factory embedded unique identifier could be embedded inthe light source/driver.

The size of the required address space makes that the preferred CLmodulation techniques, such as code division multiple access (CDMA) andfrequency division multiple access (FDMA), cannot be appliedefficiently. This is caused by the fact that these are typically limitedto, due to practical implementation issues, much smaller number ofunique codes or frequencies, for CDMA and FDMA, respectively.

WO2007/095740 discloses a light source configured to send a beaconsignal representative of the unique identifier thereof, on command,constantly or at a predetermined interval. The beacon signal isintegrated into the light emitted by the light source, wherein theintegration of the beacon signal is performed in a manner that visibleflicker of the resultant light is imperceptible. A remote detection unitis configured to receive the light and extract the beacon signaltherefrom. In this manner the remote detection device is capable ofwirelessly determining the unique identifier of a light source.

For advanced user interaction with a lighting system one wants toidentify, and estimate the strength of, the local light sources. This isenabled by CL. When worldwide or control network wide unique, andconsequently long, addresses or codes are applied, however, efficient CLmodulation methods cannot be applied to their best extent. This resultsin a long response time of the system, which might turn out to beunacceptable for some applications. Also, the suboptimal assignment ofaddresses or codes between the light sources might result in decreasedperformance in illumination contribution estimation.

Furthermore, the number of addresses needed to identify a light sourceglobally may be two orders larger than what is needed to control thelight sources in the local proximity or in a room.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the problemsdiscussed above, and to provide improved means for operating a lightingsystem.

Generally, the above objectives are achieved by a remote controller, alighting system, and a method for assigning an identity, according tothe attached independent claims.

According to a first aspect, the above objects are achieved by a remotecontroller comprising a receiver for receiving coded light from a lightsource in a coded lighting system, the coded light comprising an initiallight source identifier of the light source; a processing unit forassigning a modified light source identifier to the light source basedon the received coded light; and a transmitter for transmitting themodified light source identifier to the light source. The modified lightsource identifier differs from the initial light source identifier.

By providing a remote controller capable of receiving informationpertaining to an initial identifier and assigning a modified identifieran improved (method of operating a) lighting system may be achieved. Thedisclosed remote controller may enable an efficient assignment ofidentifiers in a lighting system. The efficient assignment ofidentifiers may enable faster response time in a lighting system. Thisfaster response would create a more natural interaction with thelighting system for the user. Moreover the remote controller allows asmaller set of addresses to be applied in a lighting system. Theaddresses might be reused by different luminaires. Thereby a moreefficient system requiring less complexity in the luminaires and remotecontrollers may be created. Also, the efficient assignment of addressesmay yield more accurate estimation of illumination contributions of theindividual light sources and reliable detection of the luminaireidentities by the remote controller. Moreover, by using such a remotecontroller the need for multiple access technique or synchronization tobe applied when the initial identifier is used may be reduced or eveneliminated, which may reduce the complexity of the system.

The initial light source identifier may correspond to a world uniqueaddress identifier of the light source, e.g. associated with a serialnumber or other factory control information. Thereby the origin of thelight source may be traceable. Thereby the light source may be uniquelyidentifiable.

The modified light source identifier may correspond to a unique addressidentifier of the light source in the coded lighting system. That is,the modified light source identifier may correspond to a local areaaddress identifier of the light source.

The coded light comprising the initial identifiers may be transmittedusing an initial access method. The processing unit may be arranged toassign a modified access method to the light source based on thereceived coded light. The transmitter may be arranged to transmit themodified access method to the light source. The initial access methodmay differ from the modified access method.

The coded light comprising the initial identifiers may be transmittedusing an initial modulation method. The processing unit may be arrangedto assign a modified modulation method to the light source based on thereceived coded light. The transmitter may be arranged to transmit themodified modulation method to the light source. The initial modulationmethod may differ from the modified modulation method.

Thus the access method and/or modulation method of the at least onelight source may depend on the identifier. Thereby the access methodand/or modulation method may be adapted to the conditions of the emittedlight inter alia as received by a receiver.

The processing unit may be arranged to generate the modified lightsource identifier to be of a length being different from the length ofthe initial light source identifier.

For example, the modified identifier may include a smaller number ofbits than the initial identifier. As illustrated in FIG. 7, the modifiedidentifier 704 has a number of bits N that is smaller than the number ofbits M of the initial identifier 702. A short modified identifier mayenable more accurate detection or reception of the same. The initialand/or modified identifiers, respectively may also be associated with arespective error correcting code, wherein the error correcting code maybe adaptable to the channel conditions.

The remote controller may be arranged to utilize a different field ofview for receiving coded light comprising the modified light sourceidentifier than for receiving coded light comprising the initial lightsource identifier.

Thus, by using f.i. a narrow field of view the remote controller may beable to detect and uniquely identify a light source although theidentifier of the light source is not locally unique. As new identifiershave been assigned a wide field of view may be utilized in order toinvestigate whether or not two or more light sources are associated withthe same identifier. In addition, the remote controller may therebyachieve different angular resolutions depending on the field of view.Moreover, in the first phase applying a multiple access solution may beavoided, since the signal is only received from one light source. Anyoverhead data associated with a multiple access solution may be avoided.Another problem that may be avoided is the assignment of CDMA codes orFDMA codes, since all light sources of the lighting systems do not needto be simultaneously identifyable by the remote controller during thefirst phase. Multiple access may be desired in the second phase, sincethen it may be desirable to control the lighting system comprisingmultiple light sources. By utilizing multiple access multiple lightsources may be simulataneously identifyable. Any codes, frequencies ortime slots for multiple access can be assigned after the first phase.

The receiver may be arranged to receive coded light from at least twolight sources each emitting coded light comprising individual initiallight source identifiers. The processing unit may be arranged to assignindividual modified light source identifiers to the at least two lightsources based on the received coded light from the at least two lightsources. The individual modified light source identifiers may begenerated by redistributing at least two of the individual initial lightsource identifiers among the at least two light sources.

Thus generating a new set of identifiers may be avoided. This may enablea shorter time for assigning the modified identifiers. Theredistribution may depend on the location of the individual lightsources in a lighting system. The redistribution may involve locallyseparating identifiers of neighboring light sources, such that theidentifiers of the neighboring light sources are maximally separated.

The processing unit may be arranged to assign the modified identifierbased on at least one property of the received coded light. Thus thesecond identifier may be based on at least one from a number ofproperties of the emitted light of the at least one light source and notonly on the currently assigned identifier of the at least one lightsource. Thereby a more reliable second identifier, in terms of interalia error correcting and/or detecting capabilities and/or accuracy inillumination contribution estimation, may be assigned to the at least onlight source.

The remote controller may form part of a lighting system. According to asecond aspect, the above objects are achieved by a lighting systemcomprising a remote controller as disclosed above and a light sourceenabled to emit coded light comprising a light source identifier,wherein the light source comprises: an emitter for emitting the codedlight comprising the initial light source identifier; and a receiver forreceiving, from the remote controller, information to assign themodified light source identifier to the light source.

The emitter may be arranged to emit the coded light using an initialaccess or modulation method; the receiver may be arranged to receiveinstructions to use a modified access or modulation method, and theemitter may further be arranged to emit the coded light using themodified access or modulation method based on the instructions.

The light source may be part of a luminaire.

According to a third aspect of the present invention, the objects areachieved by a method for assigning an identity to a light source in acoded light lighting system comprising the steps of receiving codedlight from a light source in a coded lighting system, the coded lightcomprising an initial light source identifier of the light source;assigning a modified light source identifier to the light source basedon the received coded light; and transmitting the modified light sourceidentifier to the light source, wherein the initial light sourceidentifier differs from the modified light source identifier.

The assigning method according to the third aspect of the presentinvention may be implemented in a method of operating a lighting system.According to a fourth aspect of the present invention, the objects areachieved by a method of operating a lighting system comprising a remotecontroller and a light source enabled to emit coded light comprising alight source identifier, the method comprising the steps of emitting,from the light source, the coded light comprising an initial lightsource identifier; assigning a modified identifier to the light sourceaccording to the above method for assigning an identity to a lightsource in a coded light lighting system, and emitting, from the lightsource, coded light comprising the modified light source identifier.

The lighting system may comprise a plurality of light sources. Themethod may further comprise the step of emitting, from at least onelight source of the plurality of light sources, the coded lightcomprising the modified light source identifier.

Thus, as the at least one light source has been provided with a modifiedidentifier it may emit coded light comprising the modified identifier.Thereby it may be verified that the identifier of the at least one lightsource has been correctly updated.

The initial light source identifier may be used in a set-up mode and themodified light source identifier may be used in a use mode. The initialidentifier may comprise information or data which may be usable in aset-up mode. This information or data may be excluded in the use mode incase it is decided that further reassignment of the identifier is notrequired. Thereby the complexity of the identifier used in the use modemay be reduced.

For example, the modified identifier may have a number of bits in commonwith the initial identifier. Thereby an efficient procedure forassigning modified identifiers may be achieved.

The objective is thus inter alia achieved by a system, which during aninitial phase, or mode, uses an initial set of addresses, which may belong addresses and which may be unique throughout the system or theentire world. During a second phase, or mode, however, the system usesmore efficient identification, access and/or modulation methods thatonly require local uniqueness and enables the use of wide field of viewoptical sensors.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

It is noted that the invention relates to all possible combinations offeatures recited in the claims. Thus, in general, the second, third, andfourth aspects may have the same advantages as the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be describedin more detail, with reference to the appended drawings showing acurrently preferred embodiment of the invention.

FIG. 1 is a lighting system according to an embodiment of the presentinvention.

FIG. 2 is a light source in the system in FIG. 1.

FIG. 3 is a remote controller in the system in FIG. 1.

FIGS. 4-6 are flowcharts according to embodiments of the presentinvention.

FIG. 7 is a block diagram illustrating an example of an initial lightsource identifier and an example of a modified light source identifieraccording to embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which certain embodiments areshown. This invention may, however, be embodied in many different formsand should not be construed as limited to the embodiments set forthherein; rather, these embodiments are provided by way of example so thatthis disclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Like numbers referto like elements throughout.

Operation of a lighting system will now be disclosed with reference tothe lighting system 100 of FIG. 1. The lighting system 100 comprises atleast one light source, schematically denoted by the reference numeral102.

It should be noted that the term “light source” means a device that isused for providing light in a room, for purpose of illuminating objectsin the room. Examples of such light providing devices include lightingdevices and luminaires. A room is in this context typically an apartmentroom or an office room, a gym hall, a room in a public place or a partof an outdoor environment, such as a part of a street.

Each light source 102 is capable of emitting coded light comprising alight source identifier, as schematically illustrated by the arrow 104.Each light source 102 may be associated with a number of lightingsettings, inter alia colour, colour temperature and intensity of theemitted light.

The system 100 further comprises an apparatus 106, termed a remotecontroller, for detecting and receiving the coded light comprising thelight source identifier emitted by the light source 102. The apparatus106 comprises a light sensor 108 for detecting the light emitted by thelight source(s) in the system 100.

FIG. 2 schematically illustrates the internal components of a lightsource 200, such as the light source 102 of FIG. 1 as disclosed above.The light source 200 is thus configured to emit coded light, wherein thecoded light comprises a light source identifier of the light source 200.The light source comprises an emitter 202 for emitting the coded light.The light source 200 further comprises a receiver 212 for receivinginformation to assign a modified light source identifier to the lightsource 200. The receiver 212 may be a receiver configured to receivecoded light. The receiver 212 may comprise an infrared interface forreceiving infrared light. Alternatively the receiver 212 may be a radioreceiver for receiving wirelessly transmitted information. Yetalternatively the receiver 212 may comprise a connector for receivinginformation transmitted by wire. The wire may be a powerline cable. Thewire may be a computer cable. The light source 200 may further compriseother components such as a processing unit 208, a memory 210, an encoder206 and a modulator 204 operated according to principles which as suchare known to the skilled person. The processing unit 208 may comprise acentral processing unit (CPU). Particularly, the processing unit 208 maybe operatively connected to the receiver 212. The processing unit 208may thus receive information from the receiver 212 pertaining toassigning a modified identifier to the light source 200. Based on thisinformation the processing unit 208 may request the encoder 206 tochange the encoding of the coded light such that the coded lightcomprises the modified identifier. The encoder 206 may comprise a pulsegenerator. Information pertaining to the identifiers, such as codeparameters used by the encoder 206, may be stored in a memory 210. Theupdated code sequence, as generated by the encoder 206, may then beutilized by the modulator 204 which is configured to modulate the light.The modulator 204 may comprise an intensity controller. The coded andmodulated light may then be emitted by the emitter 202. The emitter maybe a light emitting diode or the like. At least one light source 200 maybe comprised in a luminaire (not shown). Thus such a luminaire maycomprise at least one light source 200, wherein each light source may beassigned individual light source identifiers.

FIG. 3 schematically illustrates the internal components of a remotecontroller 300, such as the remote controller 106 of FIG. 1 as disclosedabove. The remote controller 300 comprises a receiver 302 for receivingcoded light from at least one light source, such as the light source102, 200. The remote controller 300 is further configured to detect aninitial light source identifier comprised in the received coded lightand being associated with a light source. The identification of thelight source identifier may be performed in a processing unit 304. Theprocessing unit 304 may comprise a central processing unit (CPU). Theprocessing unit 304 is further configured to assign a modified lightsource identifier to the light source associated with the received codedlight based on the received coded light. The processing unit 304 may beconfigured to estimate or determine at least one property of the lightsource emitting the coded light and/or at least one property of thelight emitted by the light source. The remote controller 300 furthercomprises a transmitter 312 for transmitting the modified light sourceidentifier to the light source. The remote controller 300 may furthercomprise other components such as a memory 306, an encoder 308 and amodulator 310 operated according to principles which as such are knownby the skilled person. Particularly, the memory 306 may comprise a setof identifiers, or addresses which may be transmitted to light sourcesin a lighting system. The memory 306 may comprise stored instructionspertaining to generating a set of identifiers, or addresses. The memory306 may comprise stored instructions pertaining to identification oflight sources from the received coded light. The transmitter 312 may bea light transmitter configured to emit coded light. Alternatively thetransmitter 312 may be a radio transmitter configured to wirelesslytransmit information. The transmitter 312 may be configured forbidirectional communications. The transmitter 312 may comprise a radioantenna. Alternatively the transmitter may comprise a connector forwired communications. The remote controller 300 may be configured toprovide an audible, tactile or visual feedback message when the remotecontroller detects that the light source emits coded light comprisingthe modified light source identifier (inter alia in order to signal to acommissioner that the switch from the initial light source identifier tothe modified light source identifier has been successful and that thelight source, or luminaire, is now commissioned and part of the system).

FIG. 6 is a flowchart of a method in a system, such as the lightingsystem 100, comprising a remote controller and a light source. The lightsources are assigned (individual) initial identifiers, step 602. Theinitial identifiers may be assigned during manufacturing of the lightsources. The initial identifiers may be associated with a manufacturingcode, a control number, a serial number, or the like, of the lightsource. That is, the initial identifiers may be factory settings.Alternatively, the initial identifiers may be randomly generated (by thelight source). Each light source is capable of emitting coded light,step 604, comprising the light source identifier.

According to embodiments the coded lighting system is operable in atleast two modes, or phases, (the terms mode and phase will in thiscontext be used interchangeably) where in the first phase differentidentifiers of the light sources is applied than in the second phase.Initial identifiers are used in the first phase whereas modifiedidentifiers are used in the second phase. The modified identifiers maybe associated with more (time) efficient reception than the initialidentifiers. In the first phase, which may be an initiation phase or aset-up mode, the light sources are thus operable to emit coded lightcomprising the initial light source identifiers. The initial lightsource identifiers may correspond to world unique address identifiers ofthe light sources. That is, the initial light source identifiers maycorrespond to wide area address identifiers of the light sources. In asecond phase, which may be an operation phase or a use mode, the lightsources are operable to emit coded light comprising the modified lightsource identifiers, wherein the initial light source identifiers differfrom the modified light source identifiers. The modified light sourceidentifiers may correspond to unique identifiers of the light sources inthe system. That is, the modified light source identifiers maycorrespond to local area address identifiers of the light sources. Thus,after reception, by the remote controller, of the coded light comprisingthe initial identifier, step 606, the remote control is operable toassign modified identifiers to the light sources associated with thelight received by the remote controller, step 608. The remote controlleris furthermore operable to communicate the modified identifiers to eachindividual light source in the lighting system. The light sources maythen emit the coded light comprising the modified light sourceidentifiers, step 610.

The remote controller may receive the coded light comprising themodified identifiers, step 612.

When the modified light source identifiers have been assigned the systemmay operate in the second phase, which may be a use mode, step 614.

The reassignment or reshuffling of modified identifiers (such asaddresses, codes, or frequencies) can be done in an iterative manner,steps 616, 618. This procedure has the advantage that it enables anadaptive optimal identifier assignment. In other words, an optimalidentifier assignment is enabled even when the location of the remotecontroller is moved during the act of controlling the system in the usemode.

Time division multiple access (TDMA) or random access (RA) solutions maybe used when the initial light source identifiers are used. RA may beimplemented according to the Aloha protocol. Particularly, the Alohaprotocol without acknowledgement may be utilized. Long identifiers, oraddresses, may result in a large reaction time, due to the limitedbandwidth of the CL channel. Such long reaction times might beacceptable for initial commissioning, system setup or systemconfiguration, but might not be acceptable for user interaction in scenesetting or other more advanced applications, such as applied in the usemode.

Since a light source and its corresponding identifier may identify aposition, the coded lighting system may be utilized for positioningapplications. For example, the coded lighting system may be utilized forproviding positional information in a building, thereby inter aliaproviding means for finding a user's way in the building. For such anexample it may be desirable to utilize a remote controller having a widefield of view and therefore locally unique identifiers may be desirable.

According to embodiments, the length of the modified light sourceidentifiers may be different from the length of the initial light sourceidentifiers. Particularly, the length of the modified light sourceidentifiers may be shorter than the length of the initial light sourceidentifiers. This enables a shorter acquisition and resulting systemresponse time. The operation mode in the second mode may enableapplications in the area of lighting controls, such as scene setting,which might not be possible with the response times in the first mode.The second mode may also include control loops, which may requireadditional sequential control and measurement steps. These measurementsmay require every time to identify and estimate the contributions of alllight sources, hence the time for one measurement should be low.

As disclosed above the response time might be long when the initiallight source identifiers are used, especially in cases whenidentification or addressing by means of codes transmitted using RA isused. In such cases it may be necessary to avoid collisions betweenidentifiers from different light sources. Therefore a remote controllerwith a narrow field of view (FOV) may be applied when the initial lightsource identifiers are used where the user points the receiver to(individual light sources from) a sub-set of light sources. The selectedlight source(s) may then be assigned modified identifiers which areshorter than the initial identifiers and which might be received usingdifferent optics (with a wide FOV). The long reaction times may thus beovercome by the use of optical sensors with limited FOV, where theremote controller, firstly only observes one light source of a pluralityof light sources in the lighting system, whilst the rest of the lightsources may be suppressed by the optical solution. In such cases thelight source can continuously transmit the initial light sourceidentifier and the delay may be limited. A narrow FOV may be associatedwith a first angular resolution, whereas a wide FOV may be associatedwith a second angular resolution. The first angular resolution may behigher than the second angular resolution. That is, the remotecontroller may utilize different angular resolution for receiving codedlight comprising the initial light source identifier than for receivingcoded light comprising the modified light source identifier. Also, asdisclosed above, the first phase wherein the initial light sourceidentifiers are used may be considered a configuration step, which mayonly need to occur during installation or reconfiguration of thelighting system. Operation as disclosed with reference to the secondphase wherein the light sources emit coded light comprising the modifiedlight source identifiers may cover the normal operation and control ofthe lighting system.

According to embodiments the same modulation and/or multiple accessmethod may be used for both phases, or modes. Alternatively the codedlight emitted during the first mode may be modulated differently thanthe coded light emitted during the second mode and/or a differentmultiple access technique might be applied during the first and secondmodes, respectively. For example RA can be used in the initial phase,the outcome (such as intensity estimates and/or light sourceidentification) of which may be used in the second phase to assignmodified light source identifiers associated with a second multipleaccess method. The second multiple access method could inter alia beCDMA based, where different spreading code words are assigned to thedifferent light sources observed in the first phase. Practical CDMAsystems can only assign a limited number of code words. The same holdsfor TDMA and FDMA, where the identified light sources in an environmentare assigned timeslots and operation frequencies, respectively, thetotal number of which is also limited. As disclosed above, for theoperation in the second phase the identifiers only need to be locallyunique (i.e. the identifiers or addresses are not longer world/controlnetwork-wide unique), depending on the foreseen application. As anexample, a locally unique identifier may be an identifier which,according to the remote controller, is unique for a particular lightingsystem. The remote controller may be capable of storing informationpertaining to a plurality of lighting systems.

The assignment for the second phase may use not only the initialidentifiers, or addresses, of the identified light sources during thefirst phase, but also additional information acquired during the firstphase. For example, the additional information may pertain toinformation, such as data, comprised in the transmitted light, asfurther disclosed below. Also, this information could be the estimatedrelative intensities. Also the relative location of the light sourcescan be used, inter alia as found by using a multiple diode based photosensor or camera solution in the receiver. For the FDMA embodiments, asan example, this may be of interest, since neighboring frequencies maynot yield full orthogonality. This is caused by limited acquisition timeand frequency inaccuracies of the frequency sources. The further twofrequencies applied by two light sources are separated (i.e. the largerthe frequency difference between the two frequencies applied by twolight sources), the better they can be identified. Consequently,neighboring light sources, as identified in the first phase, may beassigned frequencies that are not adjacent. The same holds for CDMAcodes, where “most orthogonal” codes be assigned to neighboring lightsources. As an effect not only the acquisition time may be decreased,but also the estimation accuracy and correct identifier detectionprobability for the application may be increased.

Also other relative properties of the light sources may be utilized. Anestimation of a relative property may involve estimating the absolute,or individual, properties of two or more light sources. Relativeproperties may be deduced from comparing absolute properties. Theassigning may thus be based on at least one property of the receivedcoded light. The at least one property may be illumination contribution.The at least one property may be radiation contribution. The at leastone property may be light color. The at least one property may bewavelength. The at least one property may be angle. The at least oneproperty may be the position of the at least one light source in thelighting system. The at least one property may be relative properties ofthe above properties, such as relative illumination, radiation, color,wavelength, angle, and/or position. The at least one property may be acombination of at least two of the above properties, and/or relativeproperties. Alternatively, the property may be based on otherinformation embedded in the coded light during the first phase. Forexample the data may be associated with description of the light source,such as its size, lumen output, emitted colour of light, or the like.Thus one advantage may be that the remote controller may not need tomeasure or estimate these properties. Alternatively the remotecontroller may compare the received description of the light source withmeasured or estimated properties of the light source in order to assigna suitable new, modified, identifier.

For such embodiments the same multiple access method can be used in thefirst and second phases, where effectively a reshuffling of theidentifiers occurs. That is, the modified light source identifiers maybe generated by redistributing at least two of the initial light sourceidentifiers among the light sources.

According to embodiments the first phase (i.e. operation in the set-upmode) may be omitted. Each light source may choose, or be assigned, ashort random initial identifier from a pool of available random initialidentifiers. This could also be accomplished by applying a specificfunction to the (wide-area) unique initial identifiers to obtain theshort (local-area) modified identifiers. During the second phase eachlight source may communicate its chosen identifier via the emittedlight. The remote controller may observe the addresses comprised in thelight emitted by the light sources. The CL receiver may then communicateinformation requesting an acknowledgement from all light sourcesassociated with this identifier. Hence, if two of more light sourcesreply, multiple light sources have chosen the same random identifier.The conflicting light sources may then be assigned new non-overlappingidentifiers. Alternatively, the conflicting light sources may berequested to randomly pick new identifiers. The procedure is repeateduntil all light sources have different short identifiers. Alternativelythe remote controller communicates over a control network the observedidentifiers whilst the corresponding light sources identify themselvesover the control network with their identifiers. A system master maysuggest the new non-overlapping identifiers. Alternatively, the systemmaster may have an overview of the short identifier selection of all thelight sources in a memory. Thereby the system master may verify thatthere is no identifier overlapping.

A first remote controller may read the initial identifiers of thelighting system, whereas the modified identifiers may be assigned by asecond remote controller. The first remote controller may communicateits findings, such as the initial and/or modified identifiers, to thesecond remote controller (and vice versa).

Next a procedure for assigning modified identifiers will be provided.The following notation for time scales will be useful: T1 represents thefinest time resolution that can be used for switching on and off thelight source. In other words, T1=1/f, where f is the clock frequency ofthe light source, such as the clock frequency of a light emitting diodecapable of achieving a throughput of f bits per second for binarymodulation. For example, T1 may be a few tens of nanoseconds, yet forillumination control applications it can often be sufficient to clockthe light source at about 1 microsecond. T2 represents the duration ofan interval during which one on and one off switching operation of thelight source may be accommodated. A period T2 is called a frame.T2=N1*T1, where N1 is an integer. T3 represents the time interval usedfor the transmission of one user symbol (a certain code or light sourceidentifier, for example the digital code 0110), or for one measurementof the illumination contribution. T3=N2*T1, where N2 is an integer.According to embodiments the light source receives a T1 clock, but thelight source may not necessarily be aware of the timing of the T2 or T3layers. In other words, all light sources may have a perfect clock forT1 (i.e. the frequency is perfect, but the phase may be random). Thelight source may use the alternating 1010101 . . . -code in theWalsh-Hadamard (WH) set and an arbitrary time position xi in the N1frame to generate the initial identifier of the light source. Since thealternating code is shift invariant, a T3 phase offset will not matter.The remote controller detects this signal, and in particular measuresits phase offset in the T2 block. After reception of this signal, theremote controller assigns a (delta to a) new position xo in order togenerate the modified identifier. The light source starts sending a synccode, such as 111110000, and the remote controller sends the (delta to)the start of the T2 interval. The remote controller may then send a newoffset in the T2 block, and assign one of the other usable WH codes,referred to as yi, to the light source and transmits the correspondingnew pair xi, yi, thereby completing the generation of the modifiedidentifier. The system may then operate in a use mode. During the usemode each light source thus has its own unique value xi, yi and henceeach light source has its own unique modified identifier. Although twolight sources may have either the same xi or the same yi, they may nothave identical pairs xi, yi. More generally, a clock timing offsetreference may be generated in the switch from the installation mode tothe use mode. Thus according to embodiments, in the first phase, ormode, the coded light emitted by the light source may not be insynchronization with the remote controller, whereas in the second phase,or mode, the coded light emitted by the light source is insynchronization with the remote controller. In other words, according toembodiments the coded light emitted by the light source is insynchronization with the remote controller exclusively in the secondphase, or mode.

FIG. 4 is a flowchart of a method in a light source, such as the lightsources 102 and 200 of FIGS. 1 and 2 as disclosed above, for assigningan identity to the light source. The method comprises in a step 402emitting, from the light source, coded light comprising an initial lightsource identifier. In FIG. 1 this is indicated by reference numeral 104.The light is emitted by the emitter 202 of the light source 200. Themethod further comprises in a step 404 receiving, by the light source,information to assign a modified light source identifier to the lightsource, wherein the received information is based on the emitted codedlight. In FIG. 1 this is indicated by reference numeral 110. The lightis received by the receiver 212 of the light source 200. The method maycomprise in a step 406 emitting, from the light source, coded lightcomprising the modified light source identifier. As disclosed above themethod may be iterated; the light source may receive further informationpertaining to assignment of a further modified identifier, and so on, asindicated by the feedback loop represented by the reference numeral 408.

FIG. 5 is a flowchart of a method in a remote controller, such as theremote controllers 106 and 300 of FIGS. 1 and 3 as disclosed above, forassigning an identity to a light source, such as the light sources 102and 200 of FIGS. 1 and 2 as disclosed above. The method comprises in astep 502 receiving, from a light sources, coded light comprising aninitial light source identifier. The light is received by the receiver108, 302 of the remote controller 106, 300. The method further comprisesin a step 504 assigning a modified light source identifier to the lightsource based on the received coded light. The assignment may beperformed in a processing unit 304 of the remote controller 300. In astep 506 the modified light source identifier is transmitted from theremote controller to the light source. The modified light sourceidentifier may be transmitted by the transmitter 312 of the remotecontroller 300. As disclosed above the method may be iterated; theremote controller may assign a further modified identifier based on thereceived light, and so on, as indicated by the feedback loop representedby the reference numeral 508.

The person skilled in the art realizes that the present invention by nomeans is limited to the embodiments described above. On the contrary,many modifications and variations are possible within the scope of theappended claims.

The invention claimed is:
 1. A remote controller comprising: a receiverfor receiving coded light from a light source in a coded lightingsystem, said coded light comprising an initial light source identifierof said light source; and a processing unit for assigning a modifiedlight source identifier to said light source based on the received codedlight such that said modified light source identifier replaces saidinitial light source identifier and is composed of less data than theinitial light source identifier; and a transmitter for transmitting saidmodified light source identifier to said light source.
 2. The remotecontroller according to claim 1, wherein said initial light sourceidentifier corresponds to a world unique address identifier of saidlight source.
 3. The remote controller according to claim 1, whereinsaid modified light source identifier corresponds to a unique addressidentifier of said light source in said coded lighting system.
 4. Theremote controller according to claim 1, wherein said coded lightcomprising said initial light source identifier is transmitted using aninitial access or modulation method; wherein said processing unit isarranged to assign a modified access or modulation method to said lightsource based on the received coded light; said transmitter is arrangedto transmit instructions to said light source to use said modifiedaccess or modulation method, and wherein said modified access ormodulation method differs from said initial access method.
 5. The remotecontroller according to claim 1, wherein said remote controller isarranged to utilize a different field of view for receiving coded lightcomprising said modified light source identifier than for receiving thecoded light comprising said initial light source identifier.
 6. Theremote controller according to claim 1, wherein said receiver isarranged to receive coded light from at least two light sources emittingcoded light comprising individual initial light source identifiers;wherein said processing unit is arranged to assign individual modifiedlight source identifiers to said at least two light sources based on thereceived coded light from the at least two light sources; and whereinsaid individual modified light source identifiers are generated byredistributing at least two of the individual initial light sourceidentifiers among said at least two light sources.
 7. The remotecontroller according to claim 1, wherein said processing unit isarranged to assign said modified identifier based on at least oneproperty of said received coded light, wherein said at least oneproperty is at least one from the group of illumination contribution,relative illumination contribution, radiation contribution, relativeradiation contribution, light color, wavelength, angle, relative angle,and relative position of said light source in said lighting system.
 8. Alighting system comprising the remote controller and the light sourcerecited in claim 1, wherein said light source comprises: an emitter foremitting said coded light comprising said initial light sourceidentifier; and a receiver for receiving, from said remote controller,information to assign said modified light source identifier to saidlight source.
 9. The lighting system according to claim 8, wherein saidemitter is arranged to emit said coded light using an initial access ormodulation method; said receiver is arranged to receive instructions touse a modified access or modulation method, and said emitter is furtherarranged to emit said coded light using said modified access ormodulation method based on said instructions.
 10. The remote controlleraccording to claim 1, wherein said processing unit is configured toassign said modified light source identifier based on a lightingcontribution of said light source.
 11. The remote controller accordingto claim 10, wherein said lighting contribution includes at least one ofillumination contribution, relative illumination contribution, radiationcontribution, relative radiation contribution, light color, wavelength,angle, relative angle, or relative position of said light source.
 12. Amethod for assigning an identity to a light source in a coded lightlighting system, comprising the steps of: receiving coded light fromsaid light source, said coded light comprising an initial light sourceidentifier of said light source; assigning a modified light sourceidentifier to said light source based on the received coded light suchthat said modified light source identifier replaces said initial lightsource identifier and is composed of less data than the initial lightsource identifier; and transmitting said modified light sourceidentifier to said light source.
 13. The method according to claim 12,wherein the method is performed to operate the lighting system, saidlighting system comprising a remote controller and the light source,said method further comprising the steps of: emitting, from said lightsource, said coded light comprising the initial light source identifier;replacing said initial light source identifier with said modified lightsource identifier in said light source; and emitting, from said lightsource, coded light comprising said modified light source identifier.14. The method according to claim 12, wherein said assigning themodified light source identifier to said light source is based on alighting contribution of said light source.
 15. The method according toclaim 14, wherein said lighting contribution includes at least one ofillumination contribution, relative illumination contribution, radiationcontribution, relative radiation contribution, light color, wavelength,angle, relative angle, or relative position of said light source.